In some shotguns in use today, especially of the semi-automatic and pump action type, multiple shotgun cartridges are loaded into a single, stationary magazine tube, generally positioned below and parallel to the shotgun barrel. Charging the weapon is usually accomplished by inserting a first live cartridge into the weapon's chamber through the ejection port and then chambering the cartridge by releasing the bolt. With the shotgun safety engaged, additional cartridges may be loaded into the magazine through the downwardly-biased loading tray located on the bottom of the weapon directly below the chamber. While loading a tube-type magazine, one must first overcome the downward pressure exerted by the loading tray and then push the cartridge forward in the tube against the bias of a magazine tube spring. The magazine tube spring asserts continuous pressure on the loaded cartridges, urging them toward the rear of the gun to be chambered into the barrel by a bolt after the weapon ejects a previously fired cartridge.
In a typical sporting shotgun having a tube magazine, the total capacity of the tube magazine may be up to 8 (but sometimes more), depending upon the design and length of the barrel. In a special sporting or tactical shotgun for use in no round limitation hunting or by military and law enforcement units, shorter shotguns may be preferable to accommodate tighter operating environments, in other words, during close combat situations. Unfortunately, a shorter tactical shotgun necessarily has a shorter tubular magazine length and thus is typically limited to 6 or 7 cartridges or even less, thereby reducing the reserve firepower available to the operator of the weapon. This is not desirable because in the time it takes to reload a limited capacity weapon, the user may be vulnerable to the opposing target of interest or otherwise lose the opportunity to engage the target.
Attempts in the firearms industry have been made to overcome some of the drawbacks to a lower capacity shotgun. One approach has been to increase a weapon's capacity by adding a box magazine extending from beneath the gun, for example, as shown in U.S. Pat. No. 4,864,759, issued to Crossman. While this appears to provide additional capacity proportional to the length of the magazine, it introduces the tactical disadvantage of the weapon becoming more cumbersome to handle in tight quarters. Thus, the increased capacity may be outweighed by the difficulty in being able to maneuver freely while wielding the weapon.
Others have attempted to overcome the lower capacity issue by fitting a shotgun with either a rotary drum magazine, such as shown in U.S. Pat. No. 7,806,036, issued to Cook et al., U.S. Patent Publication No. 2010/0293830, submitted by Winge, or multiple tube magazines operated in a rotary fashion in line with the barrel of a shotgun, as shown, for example, in U.S. Pat. Nos. 4,905,395, issued to Wagner and 5,119,575, issued to Gajdica. While appearing to increase the capacity of a tactical shotgun, it is not without introducing the increased cost and complexity associated with a rotating feed mechanism, as well as an increased risk of a malfunction stemming from the introduction of rotating parts into an otherwise generally linear cartridge feeding system.
Yet another approach to increasing the capacity of a shotgun is shown in U.S. Pat. No. 5,367,810, issued to Stead, et al., which depicts dual magazines, located side by side and pivotable upwardly, much like the barrels of a double-barreled shotgun, between operative (feeding) and inoperative (loading) positions. While this approach successfully increased the capacity of a shorter tactical shotgun from 7 or 8, to as many as 15 standard sized shotgun cartridges, the need to open the breach of the shotgun in order to load the two magazine tubes from the rear makes for a somewhat cumbersome process.
What is needed is a higher capacity magazine arrangement for use in a special purpose hunting and/or tactical shotgun that is easy to load, can be quickly loaded, simultaneously accommodates a variety of cartridge lengths and types, and loads without requiring the opening of the breach of the shotgun.